Medical implants such as leadless stimulators or sensors may be surgically, or in some instances, percutaneously delivered and implanted within tissue of the heart. The potential for detachment of a leadless stimulator or sensor from an implantation site represents a serious and possibly life-threatening event. For example, a leadless pacemaker that becomes dislodged from an implantation site in the right ventricle of the heart can exit the heart via the pulmonic valve and lodge in the lung. Thus, secure fixation of leadless implants is extremely important for successful operation of the implant as well as for the safety of the patient.
In order to secure the implant to tissue at the implantation site, the implant may include anchoring structure at a distal end thereof that must be screwed or otherwise engaged with tissue at the implantation site. The anchoring structure is typically housed within a distal end of a retractable delivery sheath or other covering during delivery of the implant to avoid injury to the patient as the implant is brought to an implantation site. The anchoring structure is typically deployed to lodge within the tissue by being distally slid and/or rotated relative to the distal end of the delivery sheath. The delivery sheath is often a somewhat rigid tubular structure and typically includes an open blunt end that may scrape or otherwise cause injury to the patient as the delivery sheath is being tracked to the implantation site. In the case of a leadless pacemaker, such a distally placed anchoring structure makes it difficult or impossible to test the implantation site for responsiveness to determine whether that area of the heart will accept pacing pulses until after the full deployment of the anchoring structure such that an electrode of the pacemaker makes contact with the heart. In addition, if the implantation site is determined to be unacceptable or less than optimal after deployment of the distal anchoring structure, it may be difficult or impossible to reposition the pacemaker without injury to the heart. Thus a need exists in the art for a delivery and anchoring apparatus and method for delivering and implanting a leadless implant in the heart that solves one or more of the deficiencies identified above.